The invention relates to tracking ink ejections from nozzles of a printhead in an ink recorder. It finds particular application in conjunction with controlling maintenance of nozzles of the printhead based on ink ejection tracking and will be described with particular reference thereto. However, it is to be appreciated that the invention is also amenable to other applications.
Ink recorders of the type frequently referred to as ink jet printers, acoustic ink printers, or liquid ink printers, have at least one printhead from which droplets of ink are directed to a recording medium. Common methods of directing the ink droplets include continuous jetting under pressure followed by electrostatic or magnetic control of the flight of the droplets; drop ejection on-demand by pressure pulse from a piezoelectric transducer, a thermally expanding liquid or solid member, focused acoustic energy, or an induced liquid-vapor transition; or, on-demand extraction of the ink from a nozzle or pool by electrostatic, magnetic or wetting forces. In the most prevalent drop-on-demand ink jet recorders, the ink may be contained in a plurality of channels within the printhead where pressure pulses that push ink out of the channels or extraction force pulses that pull ink out of the channels are used to selectively direct ink to the image receiving medium. In order to define small droplets of liquid so that high quality printing of an image may be done, the channels and, especially, the ink emitting ending nozzles of the channels, maybe narrow and have a cross-sectional area on the order of the cross-sectional area of the drops to be emitted.
In a thermal ink jet printer, pressure pulses are generated by rapidly heating ink in a small channel or chamber so that a component of the ink expansively vaporizes creating a pressure impulse that ejects ink from a nozzle in liquid communication with the channel or chamber. The ink heating pulses are usually produced by resistors located on an inner surface of the ink channels or chambers that are pulsed with sufficient electric voltage to vaporize an ink component in a portion of the ink adjacent the resistors, typically, water. Thermal ink jet printheads usually have a plurality of ink emitters and a corresponding plurality of ink heating resistors that are individually addressable by voltage pulses to heat and vaporize ink. Thus the emission of ink drops from the plurality of emitters can be electronically controlled by the timing of voltage pulses applied to the resistor heaters corresponding to each of the plurality of emitters. Following a short time duration voltage pulse to a heater, ink adjacent the heater vaporizes explosively, pushing ink out of a nozzle that is in close fluid communication with the channel or chamber where the vapor bubble has been generated. The vapor in the bubble quickly cools and transitions back to a liquid state. This transition causes the bubble to collapse to create partial vacuum pressure that pulls ink away from the emitting nozzle. This push-pull sequence causes a portion of the liquid at the nozzle to separate as a droplet and continue moving in a direction away from the nozzle and towards the recording medium. Capillary action of the ink in the narrow channels and constricted nozzle region draws ink from an ink supply reservoir thereby readying the thermal ink jet drop emitter for the next electronic command to print a drop. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. No. 4,849,774.
A carriage-type thermal ink jet printer is described in U.S. Pat. No. 4,638,337. That printer has a plurality of printheads, each with its own ink tank cartridge, mounted on a reciprocating carriage. The channel nozzles in each printhead are aligned perpendicular to the line of movement of the carriage. A swath of information is printed on the stationary recording medium as the carriage is moved in one direction. The recording medium is then stepped, perpendicular to the line of carriage movement, by a distance equal to the width of the printed swath. The carriage is then moved in the reverse direction to print another swath of information.
It has been recognized that there is a need to maintain the nozzles and channels of a printhead in an ink recorder, for example, by capping the printhead when the printer is idle for extended periods of time. Capping the printhead is intended to prevent the ink in the printhead from drying out, which could prevent ink from being properly ejected from a nozzle. There is also a need to prime a printhead before use to ensure that the printhead channels are completely filled with ink and contain no contaminants or air bubbles, and to also periodically eject ink from the nozzles of an uncapped printhead to maintain proper ink characteristics and functioning of the drop ejection process. The periodic ejection of ink from the nozzles of an uncapped printhead, also known as ink purging, is done to counteract the effects of ink component evaporation at the ink-air surface located at the ink emitting nozzle. Especially in the case of thermal ink jet inks, some ink component is necessarily vaporizable and, therefore, somewhat volatile and subject to evaporation. Purging ink periodically from a nozzle subject to evaporation serves to eliminate ink whose properties have changed due to loss of a volatile component, thereby eliminating a potential source of poor ejection performance. Maintenance stations designed to maintain printheads of various types are described in, for example, U.S. Pat. Nos. 4,855,764; 4,853,717; and 4,746,938. Various methods and apparatus for maintaining the operation of printheads are also described in the following disclosures.
U.S. Pat. No. 5,404,158 to Carlotta et al. discloses a maintenance station for an ink jet printer having a printhead with nozzles in a nozzle face and an ink supply cartridge is mounted on a translatable carriage for concurrent movement therewith. When the printer is in a non-printing mode, the carriage is translated to the maintenance station located outside and to one side of a printing zone, where various maintenance functions are provided depending upon the location of the carriage mounted printhead within the maintenance station. The printhead nozzle face is cleaned by at least one wiper blade as the printhead enters and leaves the maintenance station. Adjacent the wiper blade is a location for collecting nozzle-clearing ink droplets, followed by a capping location where a carriage actuatable cap moves into sealing engagement with the printhead nozzle face and surrounds the nozzle to provide a controllable environment therefore. A vacuum pump is interconnected to the cap by flexible hose with an ink separator therebetween. Priming is conducted when continued movement of the carriage mounted printhead actuates a pinch valve to isolate the separator from the cap and enable a predetermined vacuum to be produced therein by energizing the vacuum pump. Once the carriage mounted printhead returns to the capping location, the pinch valve is opened subjecting the printhead to the separator vacuum and ink is drawn from the printhead nozzle to the separator. Movement of the carriage mounted printhead past the wiper blade uncaps the nozzle face to stop the prime, enable ink to be removed from the cap to the separator and cleans the nozzle. The vacuum pump is de-energized and the printhead is returned to the capping location to await the printing mode of the printer.
U.S. Pat. No. 5,850,237 to Slade discloses an apparatus and method for maintaining the proper operation of an ink recorder having an printhead that prints an image on a recording medium by selectively depositing ink drops from a plurality of ink nozzles in response to image data. The ink recorder supports a plurality of performance modes and may be a color image recorder having a plurality of color inks and a plurality of ink nozzles for each color ink. A time period during printing is determined and the number of print drop commands received by each of the plurality of ink nozzles is counted during the time period. A target value for the number of print drop commands received by each nozzle is set based on a pre-determined one of the plurality of performance modes, the image data, and a characteristic of each color ink in the case of a color ink recorder. If, during the time period determined, all of the nozzles receive the appropriate target number of print commands, then a purge ink procedure is not executed and printing is not interrupted. The print quality, overall printing speed, and ink waste are optimized by utilizing all of the factors cited in setting the target values for the number of print commands to be received by each ink nozzle in order to avoid unneeded purge ink procedures.
U.S. Pat. No. 6,130,684 to Premnath et al. discloses an ink jet printer with a capping and wiping system in a maintenance station that is connected to a common vacuum source. The wiping system includes a blotter-type collection member that presents an air vent when the printhead is in a capped position. When a priming operation is initiated, the air vent route is blocked, and full pressure is applied at the capping nozzle interface.
U.S. Pat. No. 6,416,161 B1 to Berg et al. discloses a method and system for a wiper blade mechanism usable in a maintenance station of an ink jet printer, including at least one printhead cap, a scraper, a cam shaft, a drive gear mechanism, at least one wiper blade, and a spittoon.
The disclosures cited above demonstrate that the need, devices and methods for periodically ejecting purge ink droplets from an ink recording printhead in order to maintain acceptable performance are recognized. However, periodic ink purging for maintenance purposes has the drawbacks of interrupting printing in certain circumstances, using valuable ink for non-printing purposes, and requiring provision for removal and storage of the purged ink. Therefore an ink recorder is needed that optimally balances the advantages to printhead maintenance of ink periodic purging with other important recorder performance attributes such as overall printing speed, minimum waste of printing ink, and minimum space and mechanism requirements to manage purged ink.
The appropriate frequency of ink purging is related to the properties of the ink compositions being used, many printhead parameters, environmental factors such as temperature and humidity, and the desired print quality. For a given set of ink, printhead and environmental parameter values, the frequency of ink purging can be decreased at the expense of more variation in drop ejection performance attributes such as drop velocity, direction and volume. Such variations, in turn, cause print quality imperfections arising from misplaced and incorrectly sized ink spots.
In color ink recorders, a plurality of inks are used, for example, black, cyan, magenta, and yellow inks. Each of these inks may have a different response to the frequency of ink purging. And, also, the overall affect on the quality of the color image may be different for different amounts of misplaced and incorrectly sized ink spots of the different individual color inks.
Thus, there is a particular need for increasing the throughput of an ink recorder and conserving ink by reducing printhead maintenance activities during printing. The invention contemplates a method of ink ejection tracking for controlling printhead maintenance that overcomes at least one of the above-mentioned problems and others.
In one aspect of the invention, an ink recorder for receiving raster print data and printing an image on a recording medium corresponding to the raster print data received is provided. The ink recorder includes: a printhead with a plurality of ink ejecting nozzles arranged in a single column; a print controller with a first and a second raster buffer; a first and a second stroke buffer; a DMA channel interconnecting the raster buffers and the stroke buffers; a print engine in communication with the stroke buffers and the printhead; and a maintenance controller in communication with the DMA channel and the print controller, wherein the maintenance controller monitors the DMA channel for the print data blocks communicated from the raster buffers to the stroke buffers, and communicates maintenance bypass information to the print controller.
In another aspect of the invention, a method of ink ejection tracking for controlling printhead nozzle maintenance of a printhead in an ink recorder during a print job, wherein the printhead includes a plurality of ink ejecting nozzles arranged in a single column is provided. The method includes: a) receiving input print parameters and raster print data associated with an image to be printed; b) resetting a maintenance cycle timer and a nozzle ejection buffer; c) loading a first print swath of raster print data in a first raster buffer; d) generating and storing linked print data block parameters associated with the raster print data in the first raster buffer; e) loading a second print swath of raster print data in a second raster buffer; f) loading a first stroke buffer with a first print data block from the first raster buffer via a DMA channel; g) identifying nozzle ejection signals in the first print data block communicated via the DMA channel to generate nozzle ejection information; h) storing new and accumulated nozzle ejection information in the nozzle ejection buffer; i) updating a printhead maintenance bypass status based on the stored nozzle ejection information; j) repeating steps f)-i) until the last print data block in the first raster buffer is loaded in a stroke buffer, first using a second stroke buffer, then alternating between the first and second stroke buffers; k) if the print job is complete, performing a completion procedure, otherwise, repeating steps d)-j) until the maintenance cycle timer expires, first generating print data block parameters for the raster print data in the second raster buffer, then alternating between the first and second raster buffers; l) after the maintenance cycle timer expires, determining the condition of the printhead maintenance bypass status to check if printhead maintenance may be bypassed; and m) if printhead maintenance may be bypassed, resetting the maintenance cycle timer and the nozzle ejection buffer and repeating steps d)-l), otherwise, performing periodic printhead maintenance, resetting the maintenance cycle timer and the nozzle ejection buffer, and repeating steps d)-l).
In another aspect of the invention, a method of ink ejection tracking for controlling printhead nozzle maintenance of a printhead during a print job in an ink recorder that prints an image using a plurality of color inks, wherein the printhead includes a plurality of ink ejecting nozzles arranged in a single column, wherein the single column of nozzles in the printhead includes a segment of active nozzles associated with each color ink and one or more inactive nozzles between each adjacent segment is provided. The method includes: a) receiving input print parameters and raster print data associated with an image to be printed; b) resetting a maintenance cycle timer and a nozzle ejection buffer; c) loading a first print swath of raster print data in a first raster buffer associated with a first color ink and a third raster buffer associated with a second color ink; d) generating and storing linked print data block parameters associated with the raster print data in the first raster buffer and the third raster buffer; e) loading a second print swath of raster print data in a second raster buffer associated with the first color ink and a fourth raster buffer associated with the second color ink; f) loading a first stroke buffer with a first print data block from the first raster buffer and a first print data block from the third raster buffer via a DMA channel; g) identifying nozzle ejection signals in the first print data blocks communicated via the DMA channel to generate nozzle ejection information; h) storing new and accumulated nozzle ejection information in the nozzle ejection buffer; i) updating a printhead maintenance bypass status based on the stored nozzle ejection information; j) repeating steps f)-i) until the last print data blocks in the first and third raster buffers are loaded in a stroke buffer, first using a second stroke buffer, then alternating between the first and second stroke buffers; k) if the print job is complete, performing a completion procedure, otherwise, repeating steps d)-j) until the maintenance cycle timer expires, first generating print data block parameters for the raster print data in the second and fourth raster buffers, then alternating between the first/third raster buffers and the second/fourth raster buffers; l) after the maintenance cycle timer expires, determining the condition of the printhead maintenance bypass status to check if printhead maintenance may be bypassed; and m) if printhead maintenance may be bypassed, resetting the maintenance cycle timer and the nozzle ejection buffer and repeating steps d)-l), otherwise, performing periodic printhead maintenance, resetting the maintenance cycle timer and the nozzle ejection buffer, and repeating steps d)-l).
Benefits and advantages of the invention will become apparent to those of ordinary skill in the art upon reading and understanding the description of the invention provided herein.